Such identification and counting are important in numerous fields such as the pharmaceutical industry, the agri-food industry, medical premises, hygiene services, veterinary services, site surveillance, etc; with the dimensions of the particles and microorganisms that are to be collected lying in the range 0.5 micrometers (μm) to several tens of micrometers.
Devices of this type are known from document FR-A-2 855 831 or from document FR 2 905 379 in the name of the Applicant, which devices comprise a removable centrifuging enclosure containing a collection liquid and associated with air suction means. The enclosure has an air inlet and an air outlet, and it forms a container for transporting a liquid sample containing the collected particles and microorganisms.
Those devices are self-contained, and although they are portable, they are nevertheless relatively bulky. In operation, the flow rate of air passing through the enclosure is relatively large, i.e. greater than 100 liters per minute (L/min). The air flow rate is a function of the application, and in general it is determined so as to take reliable and representative samples in a few minutes.
People who are to move about in a contaminated atmosphere or who are confronted with nuclear, biological, and/or chemical risks are required to wear respiratory protection appliances that may be fitted with filter means for purifying ambient air by filtering it.
Such appliances may be free ventilation appliances, with air passing through the filters solely as a result of the user breathing, or they may be assisted ventilation appliances with the ambient air being sucked in through filters with the help of motorized means.
Known respiratory appliances are not suitable for analyzing the atmosphere in which the users have been moving. When it is desired to perform such an analysis, the user must carry a dedicated collector device, of the type described in the above-mentioned documents FR-A-2 855 831 and FR 2 905 379, and make the device operate in situ, which is not always possible in certain contexts.